This invention pertains to fluid bed catalytic oxyhydrochlorination of ethylene to produce 1,2 dichloroethane, commonly called ethylene dichloride (EDC), and relates specifically to improved copper catalysts and their use in an ethylene oxyhydrochlorination reaction.
The production of chlorinated hydrocarbons by oxyhydrochlorination is known to the art. A known process for oxyhydrochlorination of ethylene to produce EDC, practiced in many commercial installations throughout the world, involves the reaction in the vapor phase over a fluidized catalyst bed, of a mixture of ethylene, hydrogen chloride (HCl) and oxygen or an oxygen containing gas (e.g., air), in the manner and under the conditions generally described in U.S. Pat. No. 3,488,398 granted to Harpring et al. In this process the molar ratio of ethylene to oxygen to HCl is in the range of about 1.0 to 1.2 moles of ethylene to about 0.55 to 0.9 moles of oxygen for each 2 moles of HCl, the temperature is in the range of 200.degree. to 250.degree. C., and the pressure is in the range of 10 to 50 psi.
The typical fluidized catalyst heretofore used in oxyhydrochlorination reactions consists of about 2% to 12% by weight of a copper compound, preferably copper chloride, as the active catalytic ingredient, uniformly deposited on fine particles of a fluidizable support. The support could be silica, kieselguhr, clay, fuller's earth, or preferredly alumina. The alumina support material can be gamma alumina, alpha alumina, the so-called microgel aluminas or other forms of "activated" alumina, of such a nature and particle size to be readily fluidizable without excessive catalyst loss from the reaction zone, and having the proper bulk density, resistance to attrition and particle size distributions. In the oxyhydrochlorination of ethylene, the alumina support typically used is gamma alumina having a surface area in excess of 50 m.sup.2 /g.
The standard ethylene oxyhydrochlorination catalyst, as above described, can desirably be improved in two significant respects.
First, it is desirable for the catalyst to effect a higher EDC efficiency based on ethylene (i.e., for the ethylene reactant to be more completely converted to EDC with less being converted to carbon oxides such carbon monoxide and carbon dioxide). In a high volume business such as the manufacture of EDC, small efficiency increases are very valuable. For example, in a one billion pound per year EDC plant, an EDC efficiency increase of only 1% results in a savings of about one million dollars annually. Increased EDC efficiency is particularly desirable if the ethylene oxyhydrochlorination process, as described in the Harpring et al patent (which in its exemplified embodiments used air to supply oxygen), is adapted to recycle the gases which would normally be vented to the atmosphere, in order to avoid releasing hydrocarbons and chlorinated hydrocarbons to the environment. This vent gas recycle variation of the ethylene oxyhydrochlorination process is described in more detail in U.S. Pat. Nos. 4,071,572 and 4,310,713.
Secondly, the typical copper on alumina fluidized catalyst exhibits a strong tendency to develop "stickiness" during the reaction, particularly at temperatures in excess of 225.degree. C., which can cause severe disruption of process operations. This problem and a device and means for its partial control are described in U.S. Pat. No. 4,226,798 issued to Cowfer et al, and a method of controlling stickiness in such catalysts is described in copending application Ser. No. 239,806 filed on Mar. 2, 1981 in the name of Cowfer et al. Although these devices and methods are helpful, it is more practical and efficient to make catalysts which do not develop stickiness in the first place.
Finally, by way of background, it has been proposed in prior art patents to conduct oxyhydrochlorination reactions in a fluid bed in which the fluidized catalyst contains not only copper chloride but other metal chlorides like potassium chloride on the support. For example, U.S. Pat. No. 3,427,359 describes a catalyst composition for fluid-bed oxychlorination of hydrocarbons and partially chlorinated hydrocarbons consisting of copper chloride, an alkali metal chloride and a rare earth metal chloride supported on an inert carrier material, such as alpha alumina, having a surface area no greater than 10 m.sup.2 /g. Likewise, U.S. Pat. Nos. 4,069,170 and 4,124,534 and Canadian Pat. Nos. 695,895 and 701,913 teach the use of certain metal chlorides deposited with copper chloride on low surface area supports. However, when such metal chlorides are deposited on a high surface area support such as gamma alumina, and are used in a fluid bed ethylene oxyhydrochlorination process such as described above, the EDC efficiency does not improve and increased stickiness of the catalyst particles in the fluid bed occurs. Consequently the above prior art does not teach or suggest how to obtain the improvements stated above.